Array substrate of liquid crystal display device

ABSTRACT

An array substrate of a liquid crystal display device, wherein picture quality is improved without decreasing aperture ratio by providing a storage capacitor of a large capacity. The array substrate of a liquid crystal display device includes a gate line formed on an array substrate and a gate electrode diverged from the gate line. A common line composed of substantially the same material as the gate line of an opaque metal is arranged parallel to the gate line. A first electrode of a storage capacitor composed of a transparent conductive material is formed on the common line. A gate insulating film covers the gate line, the gate electrode, and the first electrode of a storage capacitor. A semiconductor layer is formed to overlap the gate electrode on the gate insulating film. A source electrode and a drain electrode are arranged with a constant interval on the semiconductor layer. A data line is connected to the source electrode and is arranged perpendicularly to the gate line. An insulating layer is formed on the data line, the source/drain electrodes, and the gate insulating film. A first contact hole is formed by removing the insulating layer so as to expose a part of the drain electrode. A pixel electrode is connected to the drain electrode through the first contact hole above the insulating layer.

This application is a divisional application of U.S. patent applicationSer. No.: 10/180,499 filed Jun. 27, 2002, now U.S. Pat. No. 6,894,735which claims the benefit of Korean Application No. P2001-040463 filed onJul. 6, 2001, each of which is hereby incorporated by reference for allpurposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly, to an array substrate of a liquid crystal displaydevice including a storage capacitor having a large capacity.

2. Discussion of the Related Art

Corresponding to a recent trend in flat panel display research, a liquidcrystal display device is widely used as a replacement medium which canovercome defects of a cathode ray tube (CRT) because of high contrastratio, ability to display a gray and dynamic screen, and low powerconsumption.

The liquid crystal display device is a switching device for applyingvoltage to a pixel region and shielding the voltage. The liquid crystaldisplay device includes an array substrate having a pixel electrodewhich is a region for transmitting light for applying a signal voltageto a liquid crystal layer; a storage capacitor for lowering a levelshift voltage and maintaining pixel information during a nonselectiveperiod of voltage application; a color filter substrate including acommon electrode for applying voltage to a liquid crystal layeraccording to a voltage difference between the pixel electrode, a colorfilter layer for displaying colors and selectively transmitting light,and a black matrix for shielding part of the light where an alignment ofa liquid crystal is not controlled; and a liquid crystal injectedbetween the array substrate and the color filter substrate.

The storage capacitor maintains a charged voltage in a liquid crystalcapacitor in a turn-off section of a thin film transistor so as toprevent a picture quality from being lowered by parasitic capacitance.The storage capacitor is divided into a storage on common and a storageon gate according to a method for forming a capacitor electrode. In theformer method, a storage capacitor electrode is additionally wired andconnected to a common electrode, and in the latter method, a part of then−1^(th) gate line is used as a storage capacitor electrode of then^(th) pixel. The latter method is also called a previous gate method.

In the storage on gate method, a separate capacitor line does not exist,thereby providing a high aperture ratio. Also, since there is nooverlapped part between a data line and a capacitor line, likelihood ofan open being formed in data line is reduced, thereby providing highyield. However, since a complete dot-inversion and a column-inversion,etc. are not realized in view of the electric charge of the pixel, apicture quality is relatively deteriorated.

On the contrary, in the storage on common method, since a capacitor lineis additionally formed, an aperture ratio is lowered, but a picturequality is enhanced. Accordingly, the storage on common method is moreappropriate in a liquid crystal display device if a problem of a lowaperture ratio is to be solved.

Hereinafter, the related art array substrate of a liquid crystal displaydevice will be explained with reference to the following drawings.

FIG. 1A illustrates a plan view of a related art liquid crystal displaydevice, and FIG. 1B illustrates a sectional view taken along line I-I′of FIG. 1A.

As shown in FIGS. 1A and 1B, a liquid crystal display device including astorage capacitor formed by the storage on common method. The deviceincludes an array substrate having a gate line crossing a data line todefine a pixel region; a switching device formed at a crossing point ofthe two lines; a pixel electrode connected to the switching device andformed in the pixel region; and a storage capacitor parallel to the gateline in a predetermined portion of the pixel region.

The array substrate will be explained in more detail with a fabricatingmethod. First, a conductive material such as Al, Al alloy, etc. isdeposited on an entire surface of a substrate 10 and patterned by aphotolithography method, so that a gate line 11, a gate electrode 11 a,and a capacitor lower electrode 11 c parallel to the gate line 11 areformed.

At this time, to obtain a storage capacitor having a large capacity, thesize of the capacitor lower electrode 11 c is set to be large.

Then, an inorganic insulating film is deposited on an entire surfaceincluding the gate line 11, thereby forming a gate insulating film 12. Asemiconductor layer 13 is then formed as an independent island shape onthe gate insulating film 12 above the gate electrode 11 a.

Subsequently, a conductive material such as Al or Al alloy is depositedon an entire surface including the semiconductor layer 13, and patternedby a lithography method, so that a data line 14 crossing the gate line11, source/drain electrodes 14 a and 14 b at both ends of thesemiconductor layer 13, and a capacitor upper electrode 14 c facing thecapacitor lower electrode 11 c are simultaneously formed.

At this time, the gate line 11 and the data line 14 cross each other,thereby defining a pixel region. Also, the gate electrode 11 a, the gateinsulating film 12, the semiconductor layer 13, and the source/drainelectrodes 14 a and 14 b are formed at crossing points of the two lines,thereby constituting a switching device. The switching device is asemiconductor layer and mainly composed of amorphous thin filmtransistor (a-si TFT) having amorphous silicon material.

Also, the capacitor lower electrode 11 c, the gate insulating film 12,and the capacitor upper electrode 14 c constitute a storage capacitor,thereby maintaining an electrified charge in a liquid crystal.

That is, as shown in FIG. 2, a parasitic capacitance Cgs is generated atan overlapped part of the gate electrode G and the source/drainelectrodes S/D. The parasitic capacitance generates a direct currentvoltage offset for an alternating current voltage, that is □V. Since thedirect current voltage offset causes effects such as a flicker, imagesticking, and unequal screen brightness, a storage capacitor is designedto reduce a variation of □V.

Especially if the capacitance of a capacitor is increased, picturequality is remarkably enhanced, which is achieved by enlarging areas ofcapacitor upper and lower electrodes. However, the larger the areas ofthe capacitor electrodes, the lower the aperture ratio, thereby limitingthe increase of in the capacitance of the capacitor.

In FIG. 2, D.L is a data line to which a signal voltage is applied, G.Lis a gate line to which an injection signal is applied, Clc is acapacitance by a liquid crystal between a pixel electrode and a commonelectrode (Vcom), and Cst is a storage capacitance formed between thecapacitor upper electrode and the lower electrode (Vst).

Referring to FIG. 1B, subsequently, benzocyclobutene (BCB) is depositedto a predetermined thickness on an entire surface including the dataline 14, thereby forming a passivation film 15. The passivation film 15is selectively removed, so that a first contact hole 17 for exposing apart of a drain electrode 14 b and a second contact hole 18 for exposinga part of a capacitor upper electrode 14 c are formed.

Then, a pixel electrode of indium tin oxide (ITO) material is formed toconnect to the drain electrode 14 b and the capacitor upper electrode 14c through the first and second contact holes 17 and 18.

Finally, though not shown, a color filter substrate including a blackmatrix, a color filter layer of R, G, and B, and a common electrode ofITO material are bonded to the array substrate on which theaforementioned patterns are formed. Also, a liquid crystal is injectedinto a space corresponding to about several micrometers between thearray substrate and the color filter substrate, thereby completing thefabrication of a liquid crystal display device.

However, the related art array substrate of a liquid crystal displaydevice has the following problems.

First, the capacity of a storage capacitor is determined by an area ofan electrode consisting of the capacitor. The more a region of thecapacitor is increased, the lower the aperture ratio. Therefore, a greatdeal of bright backlight is expended to display the same brightness,thereby increasing power consumption.

Second, corresponding to a recent trend of a high resolution of a liquidcrystal display, a size of a pixel becomes small, which results inmaking the capacity of a capacitor low. Accordingly, drivingcharacteristics of a device are lowered in such a manner that thevoltage greatly decreases and the holding ratio for off-current of aswitching device is decreased.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an array substrate ofa liquid crystal display device that substantially obviates one or moreproblems due to limitations and disadvantages of the related art.

An advantage of the present invention is to provide an array substrateof a liquid crystal display device which can improve an image quality byforming a storage capacitor of a large capacity with a transparentconductive material.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, an arraysubstrate of a liquid crystal display device includes a gate line formedon the array substrate and a gate electrode diverged from the gate line;a common line formed simultaneously with the gate line, composed of anopaque metal which is substantially the same material as the gate lineand arranged parallel to the gate line; a first electrode of a storagecapacitor composed of a transparent conductive material on the commonline; a gate insulating film covering the gate line, the gate electrode,and the first electrode of a storage capacitor; a semiconductor layerformed to overlap the gate electrode on the gate insulating film;source/drain electrodes arranged on the semiconductor layer with aconstant interval; a data line connected to the source electrode andarranged perpendicularly to the gate line; a passivation film formed onthe data line, the source/drain electrodes, and the gate insulatingfilm; a first contact hole formed by removing the passivation film so asto expose a part of the drain electrode; and a pixel electrode connectedto the drain electrode through the first contact hole above thepassivation film.

At this time, since a storage capacitor having a large area is formedwith a transparent conductive material, the aperture ratio is notlowered. Also, the storage capacitor is advantageous for high resolutionliquid crystal display devices with a storage capacitor having a largecapacity.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1A illustrates a plan view of a related art liquid crystal displaydevice;

FIG. 1B illustrates a sectional view taken along line I-I′ of FIG. 1A;

FIG. 2 illustrates an equivalent circuit diagram for a pixel;

FIGS. 3A and 3B illustrate a plan view and a sectional view of a liquidcrystal display device according to a first embodiment of the presentinvention;

FIGS. 4A to 4C illustrate a plan view and a sectional view of a liquidcrystal display device according to a second embodiment of the presentinvention;

FIGS. 5A to 5B illustrate a plan view and a sectional view of a liquidcrystal display device according to a third embodiment of the presentinvention; and

FIGS. 6A and 6B illustrate a plan view and a sectional view of a liquidcrystal display device according to a fourth embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIGS. 3A and 3B are a plan view and a sectional view of a liquid crystaldisplay device according to a first embodiment of the present invention.

The first embodiment relates to a liquid crystal display deviceincluding a capacitor lower electrode formed with a large area oftransparent material in a predetermined region of a pixel region and astorage capacitor which is in a region of a pixel electrode, wherein thecapacitor lower electrode is connected to a capacitor supplementaryelectrode having a low resistance.

At this time, the reason why the capacitor supplementary electrode isfurther included is to transmit voltage through the capacitorsupplementary electrode having a low resistance metal since a resistanceof indium tin oxide (ITO) corresponding to a material of the capacitorlower electrode is very high.

Referring to FIGS. 3A and 3B, a method for fabricating a liquid crystaldisplay device will be explained. First, a metal having a low resistancesuch as aluminum (Al), copper (Cu), tungsten (W), molybdenum (Mo),titanium (Ti), Al alloy, etc. is deposited on an entire surface of asubstrate 20 by a sputtering method, and patterned by a photolithographymethod, thereby forming a gate line 21, a gate electrode 21 a divergedfrom the gate line 21, and a capacitor supplementary electrode 21 cparallel to the gate line 21. At this time, since a material for thegate line is opaque, it is advantageous to form the capacitorsupplementary electrode 21 c as small as possible to provide a highaperture ratio of the device.

Then, a transparent conductive material such as ITO is deposited on anentire surface including the gate line 21 and patterned, thereby forminga capacitor lower electrode 29 covering the capacitor supplementaryelectrode 21 c. At this time, whereas the capacitor lower electrode 29of transparent material is formed over a large area so as to enhance thecapacity of the storage capacitor, an overlapped part with the data line24 is formed in a small area so as to prevent a parasitic capacitancewith the data line from occurring.

Meanwhile, the capacitor lower electrode 29 can be formed as a lineshape along the capacitor supplementary electrode 21 c as shown indrawings, and can be formed as an independent island shape so as tomaintain a low resistance.

Then, an inorganic insulating film such as silicon nitride (SiNx),silicon oxide (SiOx), or etc. is deposited on an entire surfaceincluding the capacitor lower electrode 29 by a sputtering method, sothat a gate insulating film 22 is formed. Also, amorphous silicon isdeposited on the gate insulating film 22 above the gate electrode 21 a,so that a semiconductor layer 23 is formed.

Subsequently, a metal of a low resistance such as Al, Cu, W, Mo, Ti, Alalloy, etc. is deposited on an entire surface including thesemiconductor layer 23, and patterned by a photolithography method,thereby forming a data line 24 crossing the gate line 21 andsource/drain electrodes 24 a and 24 b diverged from the data line 24.

Herein, the gate line 21 and the data line 24 crossing each other definea plurality of pixel regions, and the gate electrode 21 a, the gateinsulating film 22, the semiconductor layer 23, and the source/drainelectrodes 24 a and 24 b formed at the crossing points of the gate line21 and the data line 24 form a thin film transistor.

Then, an organic insulating film such as benzocyclobutene (BCB), acrylresin, or etc. or an inorganic insulating film such as SiOx, SiNx, oretc. is deposited with a predetermined thickness on an entire surfaceincluding the data line 24, thereby forming a passivation film 25. Thepassivation film 25 is then selectively removed, so that a contact hole27 for exposing the drain electrode 24 b is formed and then a pixelelectrode 26 of ITO material is formed to connect to the drain electrode24 b through the contact hole 27.

At this time, a part of the pixel electrode 26 corresponding to thecapacitor lower electrode 29 is a capacitor upper electrode andconstitutes a storage capacitor of a large capacity with the capacitorlower electrode 29 having a large area.

A storage capacitor having a low resistance and a large storage capacityis obtained by setting the transparent electrode of the storagecapacitor in a large area and by setting the opaque capacitorsupplementary electrode to be in a small area.

FIGS. 4A to 4C illustrate a plan view and a sectional view of a liquidcrystal display device according to a second embodiment of the presentinvention.

The second embodiment relates to a liquid crystal display deviceincluding a large storage capacitor having a transparent capacitor lowerelectrode in a large area and a region of a pixel electrode. The secondembodiment is different form the first embodiment in that an apertureratio becomes maximum without additionally forming the capacitorsupplementary electrode of an opaque metal.

Referring to FIGS. 4A and 4B, a method for fabricating the liquidcrystal display device will be explained. First, a metal having a lowresistance is deposited on an entire surface of a substrate 30 by asputtering method, and patterned by a photolithography method, therebyforming a gate line 31 and a gate electrode 31 a diverged from the gateline 31.

Next, an inorganic insulating film such as SiNx, or SiOx is deposited onan entire surface including the gate line 31 and the gate electrode 31 aby a sputtering method, thereby forming a gate insulating film 32. Then,pure amorphous silicon and doped amorphous silicon are consecutivelydeposited on the gate insulating film 32 above the gate electrode 31 a,thereby forming a semiconductor layer 33.

Subsequently, a metal having a low resistance is deposited on an entiresurface including the semiconductor layer 33, and patterned by aphotolithography method, thereby forming a data line 34 crossing thegate line 31 and source/drain electrodes 34 a and 34 b diverged from thedata line 34.

Herein, the gate line 31 and the data line crossing to each other definea plurality of pixel regions, and the gate electrode 31 a, the gateinsulating film 32, the semiconductor layer 33, and the source/drainelectrodes 34 a and 34 b formed at the crossing points of the gate lineand the data line form a thin film transistor.

Then, SiNx is deposited on an entire surface including the data line 34,so that an insulating film 38 for insulating the data line layer and acapacitor lower electrode 39 which will be formed subsequently, and acapacitor lower electrode 39 of ITO material is formed at apredetermined region above the insulating film 38.

Subsequently, BCB, acryl resin, SiOx, or SiNx are deposited on an entiresurface including the capacitor lower electrode 39, the data line 34,and the source/drain electrodes 34 a and 34 b with a predeterminedthickness, thereby forming a passivation film 35. Then, the passivationfilm 35 is selectively removed, so that a contact hole 37 for exposingthe drain electrode 34 b is formed. A pixel electrode 36 of ITO materialconnected to the drain electrode through the contact hole 37 is thenformed.

At this time, a region of the pixel electrode 36 opposite to thecapacitor lower electrode 39 is a capacitor upper electrode andconstitutes a storage capacitor with the capacitor lower electrode 39having a large area.

Meanwhile, besides the method for forming the capacitor lower electrode39 after the data line layer is formed, it is possible to form thecapacitor lower electrode 39 after the gate line layer is formed asshown in FIG. 4C.

FIGS. 5A to 5B illustrate a plan view and a sectional view of a liquidcrystal display device according to a third embodiment of the presentinvention.

The third embodiment relates to a liquid crystal display deviceincluding a storage capacitor having a capacitor upper electrode and acapacitor lower electrode formed with large areas at both sides of athin insulating film. Herein, the capacitor lower electrode is connectedto a capacitor supplementary electrode of a low resistance and receivesa voltage, and the capacitor upper electrode is connected to a pixelelectrode and receives a voltage.

At this time, since the capacitor lower electrode of ITO material has avery high resistance, a time for transmitting a voltage is delayed.Accordingly, a capacitor supplementary electrode of a low resistancemetal is connected to the capacitor lower electrode of ITO material totransmit a voltage.

Referring to FIGS. 5A and 5B, a method for fabricating a liquid crystaldisplay device will be explained. First, a metal having a low resistanceis deposited on an entire surface of a substrate 50 by a sputteringmethod, and patterned by a photolithography method, thereby forming agate line 51, a gate electrode 51 a diverged from the gate line 51, anda capacitor supplementary electrode 51 c parallel to the gate line 51 ina line shape. At this time, since the gate line is composed of an opaquematerial, the capacitor supplementary electrode 51 c is formed in asmall area, thereby preventing an aperture ratio from being lowered.

Then, a capacitor lower electrode 59 a is formed at a predeterminedregion including the capacitor supplementary electrode 51 c. At thistime, the capacitor lower electrode 59 a of transparent conductivematerial is formed in a large area so as to enhance a capacity of astorage capacitor. However, a part of the capacitor lower electrode 59 aoverlapped with the data line is formed in a small area so as to preventa parasitic capacitance from occurring.

Also, the capacitor lower electrode 59 a may be formed in a line shapealong the capacitor supplementary electrode 51 c, and may be formed inan independent island shape to be connected to the capacitorsupplementary electrode 51 c so as to maintain a low resistance.

Then, an inorganic insulating film such as SiNx or SiOx is deposited onan entire surface including the capacitor lower electrode 59 a by asputtering method, so that a gate insulating film 52 is formed.Amorphous silicon is then deposited on the gate insulating film 52 abovethe gate electrode 51 a, so that a semiconductor layer 53 is formed.

Subsequently, a metal of a row resistance is deposited on an entiresurface including the semiconductor layer 53, and patterned by aphotolithography method, so that a data line 54 crossing the gate line51, a source electrode 54 a diverged from the data line 54 above thesemiconductor layer 53, and a drain electrode 54 b formed above thesemiconductor layer 53 apart from the source electrode 54 a with aconstant interval are formed.

Then, a transparent conductive material such as ITO is deposited on anentire surface including the gate insulating film 52 and patterned, sothat a capacitor upper electrode 59 b facing the capacitor lowerelectrode 59 a is formed.

Subsequently, an organic insulating film such as BCB, acryl resin, oretc. or an inorganic insulating film such as SiOx, SiNx, or etc. isdeposited with a predetermined thickness on an entire surface includingthe capacitor upper electrode 59 b, thereby forming a passivation film55. The passivation film 55 is then selectively removed, so that a firstcontact hole 57 for exposing the drain electrode 54 b and a secondcontact hole 58 for exposing the capacitor upper electrode 59 b areformed and then a pixel electrode 56 of ITO material is formed toconnect to the drain electrode 54 b and the capacitor upper electrode 59b through the first and second contact holes 57 and 58.

At this time, the capacitor lower electrode 59 a of a large area isformed to connect to the capacitor supplementary electrode 51 c, thecapacitor upper electrode 59 b having a large area is formed to connectto the pixel electrode 56, and the thin gate insulating film 52 isformed between the capacitor upper electrode 59 a and the capacitorlower electrode 59 b to constitute a storage capacitor.

A storage capacitor having a low resistance and a large storage capacityis obtained by setting the transparent electrode of the storagecapacitor in a large area and by setting the opaque capacitor supplementelectrode in a small area. Also, since an insulating film between thestorage capacitor electrodes is thin, a larger storage capacity can beobtained.

FIGS. 6A and 6B illustrate a plan view and a sectional view of a liquidcrystal display device according to a fourth embodiment of the presentinvention.

The fourth embodiment relates to a liquid crystal display deviceincluding a storage capacitor having a capacitor upper electrode and acapacitor lower electrode formed having wide areas at both sides of athin insulating film. Since the insulating film between the capacitorupper electrode and the capacitor lower electrode is thin, a largerstorage capacity can be obtained. Also, since a capacitor supplementaryelectrode of an opaque metal material is not additionally formeddifferently from the third embodiment, an aperture ratio can be maximum.

At this time, the capacitor upper electrode is connected to a pixelelectrode.

Referring to FIGS. 6A and 6B, a method for fabricating a liquid crystaldisplay device will be explained. First, a metal having a low resistanceis deposited on an entire surface of a substrate 60 by a sputteringmethod, and patterned by a photolithography method, thereby forming agate line 61, a gate electrode 61 a diverged from the gate line 61.

Then, a transparent conductive material such as ITO is deposited on anentire surface including the gate line 61 and patterned, so that acapacitor lower electrode 69 a is formed. At this time, the capacitorlower electrode 69 a of a transparent conductive material is formed in alarge area so as to enhance a capacity of a storage capacitor. However,a part of the capacitor lower electrode 69 a overlapped with the dataline is formed in a small area so as to prevent a parasitic capacitancefrom occurring.

Then, an inorganic insulating film such as SiNx or SiOx is deposited onan entire surface including the capacitor lower electrode 69 a by asputtering method, so that a gate insulating film 62 is formed.Amorphous silicon is then deposited on the gate insulating film 62 abovethe gate electrode 61 a, so that a semiconductor layer 63 is formed.

Subsequently, a metal having a low resistance is deposited on an entiresurface including the semiconductor layer 63, and patterned by aphotolithography method, so that a data line 64 crossing the gate line61, a source electrode 64 a diverged from the data line 64 above thesemiconductor layer 63, and a drain electrode 64 b formed above thesemiconductor layer 63 apart from the source electrode 54 a with aconstant interval are formed.

Then, a transparent conductive material such as ITO is deposited on anentire surface including the gate insulating film 62 and patterned, sothat a capacitor upper electrode 69 b facing the capacitor lowerelectrode 69 a is formed. At this time, the capacitor upper electrode 69b is formed to be substantially the same size as the capacitor lowerelectrode 69 a so as to enhance a capacity of the storage capacitor.

Subsequently, BCB, acryl resin, SiOx, or SiNx is deposited with apredetermined thickness on an entire surface including the capacitorupper electrode 69 b, thereby forming a passivation film 65. Thepassivation film 65 is then selectively removed, so that a first contacthole 67 for exposing the drain electrode 64 b and a second contact hole68 for exposing the capacitor upper electrode 69 b are formed and then apixel electrode 66 of ITO material is formed and connected to the drainelectrode 64 b and the capacitor upper electrode 69 b through the firstand second contact holes 67 and 68.

At this time, the capacitor upper and lower electrodes 69 a and 69 bhaving large areas, and the thin gate insulating film 62 formed betweenthe capacitor upper and lower electrodes 69 a and 69 b constitute astorage capacitor.

A storage capacitor of a large storage capacity can be obtained byproviding the transparent electrodes of the storage capacitor in a largearea and by providing an insulating film between the storage capacitorthinly.

An array substrate of a liquid crystal display device according to thepresent invention has the following advantages.

First, a capacitor electrode of a large area is formed by using atransparent conductive material, thereby obtaining a storage capacitorof a large capacity.

Accordingly, a picture quality can be improved without decreasingaperture ratio.

Second, corresponding to a recent trend that a size of a unit pixelbecomes small according to high resolution of a liquid crystal display,a storage capacitor having a large capacity is formed, so that thevoltage of a liquid crystal is prevented from being lowered and aholding ratio according to off-current of a switching device isincreased.

Accordingly, a driving characteristic of a device is improved, and areliability of a high resolution liquid crystal display device isincreased.

It will be apparent to those skilled in the art than variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. An array substrate of a liquid crystal display device comprising: agate line formed on an array substrate and a gate electrode divergedfrom the gate line; a storage capacitor line composed of a transparentconductive material and arranged parallel to the gate line, wherein thestorage capacitor line has a first area and a second area, the firstarea is formed by a first width and a second area is formed by a secondwidth, the first width is wider than the second width; a gate insulatingfilm covering the gate line, the gate electrode, and the storagecapacitor line; a semiconductor layer formed to overlap the gateelectrode on the gate insulating film; source and drain electrodesarranged with a constant interval on the semiconductor layer; a dataline connected to the source electrode and arranged perpendicularly tothe gate line, wherein the data line is overlapped the second area ofthe storage capacitor; an insulating layer formed on the data line, thesource/drain electrodes, and the gate insulating film; a first contacthole formed by removing the insulating layer so as to expose a part ofthe drain electrode; a pixel electrode connected to the drain electrodethrough the first contact hole above the insulating layer; wherein thepixel electrode is overlapped the first area of the storage capacitor,wherein a length of the first area of the storage capacitor line in anextended direction is wider than that of the pixel electrode; a storagecapacitor electrode formed in the same layer as the source/drainelectrodes, arranged in the pixel electrode to overlap the first area ofthe storage capacitor line, and composed of a transparent conductivematerial; and a second contact hole which exposes a part of the storagecapacitor electrode on the insulating layer so as to be electricallyconnected to the pixel electrode.
 2. The array substrate of a liquidcrystal display device of claim 1, wherein the first width of thestorage capacitor line and a width of the storage capacitor electrodeare wider than that of the gate line.
 3. The array substrate of a liquidcrystal display device of claim 1, wherein the insulating layer iscomposed of one of SiNx, SiOx, BCB, and acryl resin.
 4. The arraysubstrate of a liquid crystal display device of claim 1, wherein thestorage capacitor line and the storage capacitor electrode are composedof indium tin oxide (ITO) or indium tin zinc oxide (ITZO).